Spend a few weeks letting him get used to you before you try putting a bridle on him. Have an experienced person do that with you the first few times, as you don't want to spook him, or accidentally hurt him.

Have you had any prior experience with horses?

You don't want a dog to eat apple seeds, but I have never heard of them harming a horse! They will probably pass right through, no harm done. We never cored any apple before giving it to a horse.